He was not throwing to drek for all three years. He had more than adequate weapons in 2016 and half of 2018, for sure. And not surprisingly, that's when he was most effective. He was an average to substandard QB when he didn't have good enough players around him. Which kind of supports the point that Dak is more bus driver than QB who makes people around him better.
Let's take a look at what other quarterbacks in the league had who are considered good quarterbacks.
In 2016,
Aaron Rodgers
Randall Cobb, Davante Adams and Jordy Nelson.
Ben Roethlisberger
Antonio Brown......Leveon Bell was a big part of the passing game.
Matt Ryan
Sanu, Julio, Gabriel...Coleman and Freeman were big parts of the passing game as well.
Kirk Cousins
Desean Jackson, Garcon and Jordan Reed.
Brady
Gronkowski, Bennett, Edelman, Hogan....James White was a big part of the passing game.
Palmer
Fitzgerald, Brown, Floyd, Nelson and Johnson.
Brees
Brandon Cooks, Michael Thomas, Willie Snead.....
Stafford
Boldin, Tate, Jones and Ebron
Rivers
Williams, Inman, Benjamin, Gates and Henry...(Allen got hurt)
I just posted the top 10 quarterbacks in 2016......let's go a little further and see who cracked the top 15.
Russell Wilson
Jimmy Graham, Doug Baldwin, Tyler Lockett, Richardson
Andy Dalton
AJ Green, Lafell, Boyd, Eifert
Flacco
Steve Smith, Mike Wallace, Pitta, Perriman
Carr
Cooper and Crabtree
Bradford
Thielen, Diggs and Rudolph
So this is the top 15 passing offenses that year and I don't see one I wouldn't take over Witten, Dez and Terrence Williams.
Mind you......I didn't even get to the Bucc's, Giants or Bronco's.......